1. Field of the Invention
The present invention relates to a color image forming apparatus wherein a color toner image is formed on a belt-shaped image retainer by an electrophotographic system and transferred to a transfer paper to form a color image.
2. Description of the Prior Art
Many kinds of color image forming apparatuses have been proposed. In the typical color image forming apparatus, a belt-shaped image retainer (photosensitive) is trained around two rollers, and a plurality of developing devices including toners different in color from one another are disposed below the lower flight of said photosensitive belt. A color image is formed on the photosensitive belt by forming latent images corresponding to the color separation number of a document image on said photosensitive belt and developing the latent images by said plural developing devices every time the latent image is formed while rotating the photosensitive belt plural times to form a color toner image, and then said color toner image is transferred at a time to a transfer paper supplied from a paper feed cassette in a cassette receiving room disposed below the plural developing devices to obtain a color copy.
In such a color image forming apparatus, U-turn of a small curvature radius of the photosensitive belt is practicable different from the photosensitive drum, so that the photosensitive belt can run along the flat plane and the space can be utilized effectively. Further, by providing a separation electrode for transfer papers to which images have been transferred at the U-turn portion of the small curvature radius, the transfer papers can be separated positively.
In said color image forming apparatus, the photosensitive belt and the cassette receiving room are disposed in the form of layers at both sides of the plural developing devices. Paper feed means and a paper feed path connecting the cassette receiving room with a transfer portion of the photosensitive belt are provided along an inner side wall of the apparatus body so as to circulate around the plural developing devices. Further, a cassette insertion port of said cassette receiving room is formed in a side wall of the apparatus body opposite to said inner side wall at which said paper feed path and paper supply means are mounted, so that the feed paper cassette can be inserted in the same direction as the paper feed direction.
However, if such a style that the feed paper cassette is inserted into the cassette receiving room from the side opposite to the side at which the paper feed path and the paper feed means are provided is employed, it is necessary to open said two opposite side surfaces of the apparatus body arbitrarily for processing jamming or the like. Accordingly, a large space for the apparatus is required and the operations of copying and the maintenance become difficult.
In order to solve the above problems, there is proposed an image forming apparatus wherein the cassette insertion port is provided on the side surface of the apparatus at which the paper feed path is provided so as to carry out from one side surface of the apparatus body all of the operations such as the insertion of the paper feed cassette and maintenance such as the processing of jamming.
The length of the peripheral surface of the photosensitive belt becomes twice longer than the distance between said two rollers, so that the photosensitive belt can have an image forming portion of a length substantially twice the distance between the two rollers.
However, in case that a transfer paper corresponding to said image forming portion is longer than the depth of the image forming apparatus, the paper feed cassette containing such long transfer paper becomes over the depth of the image forming apparatus, so that the paper feed must be carried out in a state that a portion of the cassette projects from the front surface of the apparatus body. Accordingly, the floor space for the apparatus becomes large and the cassette would disturb person's walking and operations at the inoperative state of the apparatus.